…understand place value & decimals
We use decimals as another way of writing fractions. You’ll see decimals
used most commonly in:
•
money – for example, a box of copier paper may cost £12.75
•
weights and measures – for example, a parcel may weigh 1.5 kilos.
The number to the left of a decimal point is the ‘whole number’; the number
to the right of a decimal point is the ‘decimal fraction’.
Place value
Where we place a number affects its value. This is called place value, and
it’s important for understanding decimal numbers.
Look at the number 187. We can write it down as
the result of the numbers 100, 80 and 7 added
together:
By place value, we mean that:
• the column on the right is the ‘units’ column.
These are numbers between 0 and 9
• the next column from the right is the ‘tens’ column. These are 10, 20,
30, 40, 50, 60, 70, 80, 90
• the third column is the ‘hundreds’ column. These are the hundreds from
100 to 900.
Place value and the decimal point
Take the example of 465.27.
We can show how it’s made up in the following grid:
We can see that:
• the first column to the right of the decimal point is for tenths, so the 2
2
is worth 2 tenths of one pound or £
or 20 pence
10
• the second column to the right of the decimal point is for hundredths,
7
so the 7 is £
or 7 pence.
100
Each column has a place value 10 times greater than the column to its right.
Try these!
•
Write the following numbers in grids showing place value.
a) £2.95
•
b) £10.50
c) 125.05 kg
What is the value of the 5 in each of the following? Write your answer
as a fraction of a £ and in pence.
a) £2.95
b) £10.50